OPG conducted an in-person meeting at the Barrys Bay Legion on Mon Feb 12 to provide attendees with educational resources addressing management of the Madawaska River system and to answer questions.
An OPG video was shown , Madawaska River | An overview of water management – March 2022 (youtube.com) which describes the regional OPG water management organisation, a brief description of how hydraulic electrical generation functions, and the criteria used to determine water flows and lake levels. This video presentation of 15 minutes was used as the basis for the discussion that ensued.
Educational resources | Water management – OPG provides the current and historical water flows and lake levels of the Madawaska River System (including other Ontario river systems). Select the “Eastern Ontario” dropdown for Kamaniskeg Lake and Bark Lake daily water levels.
The questions and discussions from the floor were mainly related to the operation of the Bark Lake and Palmer Rapids dams, particularly in springtime when flooding has occurred in the past.
The overriding priority for operating these dams is the prevention of flooding, and the preservation of the integrity of the dam. (If the dam were to overflow, water would pass around the sides of the dam, causing washouts, and possible dam collapse.) The required lake levels are given on the OPG website.
Drawdown of Bark Lake begins in January and typically lowers Bark Lake by about 7 meters, and is completed just before freshet. (The spring melt, typically April). The size of the spring freshet (volume of water flowing) is determined by the water content of the snow, temperature, and rainfall during the freshet.
As these parameters are not exactly known prior to the freshet, drawdown of Bark Lake is usually taken to the allowable lowest level. In a typical year there is usually enough water going into Bark Lake to fill the reservoir 2 or 3 times over if none is released. It is a balancing act, to fill Bark Lake by the May 24 weekend, and avoid flooding downstream, due to the uncertainties of the freshet, and the independent variables. Occasionally Bark Late is late to be filled, and occasionally some flooding occurs downstream. All due to the vagaries of the freshet.
The level of Bark Lake is controlled by the operation of valves at the bottom of the dam, and the removal of logs from the top of the dam. This requires staff to be dispatched from Barrett Chute Generating Station (Calabogie). There is no electrical supply at Bark Lake Dam to operate the log removals, or the valves so a generator must be started. An automated system was suggested from the floor but was rejected by OPG because of safety considerations for the downstream residents of unanticipated sudden water flow, due to remote operation.
If during the freshet, too high a water flow rate is passed from Bark Lake dam, (more than 150 cms / cubic meters per second) there is a funnel effect due to restrictions in the downstream river channel. This makes the water back up and will flood the Kamaniskeg Lake area. The valves at the bottom of Bark Lake can pass a maximum of 80cms so, log removal is required to exceed 80cms.
In the summer the usual flow out of Bark Lake is typically between 10cms and 20cms. In the summer the lake levels are relatively stable.
Submitted by Ian Doyle, Feb 13, 2024
